This invention relates generally to energy conservation in buildings and, more particularly, has reference to the use of tracer gases to measure the infiltration of air into buildings.
There is a growing need to control energy loss in homes and commercial buildings. A substantial energy loss is caused by infiltration of cold air into heated buildings during the winter and infiltration of hot air into cooled buildings during the summer. Using currently available methods, it is very difficult, time consuming, and costly to measure the amount of such infiltration and to locate the leakage points. It is especially difficult to establish an average infiltration value over an extended period of time because the leakage rate changes substantially when weather or temperature changes occur. To accomplish this using current methods requires technicans to remain in the building in question while they make repeated measurements over an extended period of time using complicated and expensive instruments.
The tracer dilution method is the most common method used today for infiltration rate measurement. It requires the release of a batch of tracer gas, usually sulfur hexafluoride. The gradual reduction in tracer gas concentration caused by air infiltration is measured at several precisely timed intervals and used to calculate the infiltration rate. This technique is very costly for making long term measurements because the expensive measurement equipment must be kept on location continuously. Its accuracy is also very dependent on the skill of the technicians who apply it in the field.
In another technique, called the constant rate method, tracer gas is injected continuously as in the present invention, but its rate of injection is varied to maintain a constant or equilibrium tracer gas concentration in the building being tested. The changes in the injection rate required to maintain the equilibrium concentration are continuously recorded and used to calculate the infiltration rate. This method also requires expensive real-time measurement instruments in the building throughout the test.